Selection of Alternative 5′ Splice Sites: Role of U1 snRNP and Models for the Antagonistic Effects of SF2/ASF and hnRNP A1
| Autor: | Javier F. Cáceres, Stephen H. Munroe, Adrian R. Krainer, Olga V. Makarova, Daniel G. Hayward, Ian C. Eperon, Akila Mayeda |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2000 |
| Předmět: |
Heterogeneous Nuclear Ribonucleoprotein A1
genetic processes Gene Expression Biology Heterogeneous ribonucleoprotein particle environment and public health Binding Competitive Models Biological Heterogeneous-Nuclear Ribonucleoproteins Ribonucleoprotein U1 Small Nuclear SnRNP binding Heterogeneous-Nuclear Ribonucleoprotein Group A-B RNA Precursors snRNP RNA Messenger Binding site Molecular Biology Ribonucleoprotein Genetics Binding Sites Serine-Arginine Splicing Factors Alternative splicing Nuclear Proteins RNA-Binding Proteins Cell Biology Cell biology Alternative Splicing Ribonucleoproteins RNA splicing health occupations RNA Splice Sites |
| Popis: | The first component known to recognize and discriminate among potential 5' splice sites (5'SSs) in pre-mRNA is the U1 snRNP. However, the relative levels of U1 snRNP binding to alternative 5'SSs do not necessarily determine the splicing outcome. Strikingly, SF2/ASF, one of the essential SR protein-splicing factors, causes a dose-dependent shift in splicing to a downstream (intron-proximal) site, and yet it increases U1 snRNP binding at upstream and downstream sites simultaneously. We show here that hnRNP A1, which shifts splicing towards an upstream 5'SS, causes reduced U1 snRNP binding at both sites. Nonetheless, the importance of U1 snRNP binding is shown by proportionality between the level of U1 snRNP binding to the downstream site and its use in splicing. With purified components, hnRNP A1 reduces U1 snRNP binding to 5'SSs by binding cooperatively and indiscriminately to the pre-mRNA. Mutations in hnRNP A1 and SF2/ASF show that the opposite effects of the proteins on 5'SS choice are correlated with their effects on U1 snRNP binding. Cross-linking experiments show that SF2/ASF and hnRNP A1 compete to bind pre-mRNA, and we conclude that this competition is the basis of their functional antagonism; SF2/ASF enhances U1 snRNP binding at all 5'SSs, the rise in simultaneous occupancy causing a shift in splicing towards the downstream site, whereas hnRNP A1 interferes with U1 snRNP binding such that 5'SS occupancy is lower and the affinities of U1 snRNP for the individual sites determine the site of splicing. |
| Databáze: | OpenAIRE |
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